In a similar fashion (for wedding bands) I can heartily recommend NIWAKA.

That's where We'll get our wedding bands if all goes well They have two shops in Tokyo (Omote Sando and Ebisu Garden Place). Check out http://www.niwaka.com to have a look. For the engagement ring you have to buy their (expensive) diamonds so I went elsewhere.

What about a weekend at the Fujiya in Miyano....a - close to Hakone. The hot mineral springs are so relaxing followed by his and hers massage. Cherry Blossom time is coming and the Fujiya Spring gardens are spectacular. Dine in private and "Pop the age old question!!"
bb

The Meguro Parasite Museum in Tokyo. It's a popular date destination in Tokyo. Really!

http://www.tmd.ac.jp/med/mzoo/MPM/mpm2E.html

Just as a follow-up. Original Plan: Tried to reserve something at the Brasserie de l'institut, but they were closed for a private party. It was probably too windy to be sitting outside yesterday anyways. On to plan 2: Since we were in Ebisu anyways, I thought about the other Brasserie there, but couldn't find their number to reserve something. Plan 3 was to reserve a place at XEX Daikanyama, which has a great rooftop terrace for when the weather is nice, but they only have an Italian restaurant and a Sushi place, and I thought to at least stick to the French theme. Plan 4: Then realized that there was a fancy French place in a replica Chateau at Yesbisu Garden Place. Somehow made me think of something they would do in Vegas, but I digress. Called them up to make a reservation, but of course they were fully booked for lunch and dinner, except for the more expensive second floor. No problem I said, although I asked if formal attire was required and metioned that I would be proposing tonight. Luckily a jacket could be provided and they gave us a nice private table. Food was excellent and service very attentive. Oh and to get to the point, she said yes

Ar! Well, first congratulations, on both your engagement, and the fact that you blindly stumbled upon what is probably one of the top 10 French restaurants in the world, the Joel Robuchon Tokyo!

Well, as long as I am filling the self-appointed role of forum architecture critic, I might as well mention that that place looks to me like a large version of the haunted mansion at Disneyland. It also doesn't match any part of the rest of the Yebisu Garden Place area.

Oh, and what happened to Taillevant, did he get bought out by Robuchon?

Do not judge a book by its cover, at least in this case. Why it looks like that, don't ask, I am at peace with such things in Japan. As for why it is only Robuchon now, well, they got into a catfight of some kind, and they decided to go their own separate ways. Taillevent has opened a couple of wine shops in Tokyo, and I wouldn't be surprised if a restaurant wasn't far off.